Solvent fractionation of waxcontaining mixtures



SOLVENT FRACTIQNATION OF'WAX-CONTAINING MIXTURES Original Filed Sept.16, 1947 ZE'ADD/TIVE EX r/v. SOLVENT HTTEST INVENTOR.

Patented Dec. 11, 1951 SOLVENT FRACTIONATION OF WAX- CONTAINING MIXTURESEdgar W. Clarke, Laurel Springs, N. J., assignor to The AtlanticRefining Company, Philadelphia, Pa., a corporation of PennsylvaniaOriginal application September 16, 1947, Serial No. 774,230. Divided andthis application November 5, 1949, Serial No. 125,725

. 5 Claims. 1

The present invention relates to the treatment of oily waxes, and moreparticularly to the separation of wax-containing mixtures into fractionsof higher and lower melting point, using a solvent comprising acetoneand an additive comprising diethylene glycol. I

This application is a division of copending application Serial Number774,230, filed September 16, 1947, and entitled Solvent Fractionation ofWax-Containing Mixtures.

The present invention is especially applicable to the deoiling ofhydrocarbon waxes containing not more than about 70% of oil, and to theseparation of wax mixtures of low oil content into fractions ofdifierent melting point. The process of the present invention may beapplied in the refining, purification, or separation of wax stocks suchas petroleum slack wax, crude microcrystalline wax, paraffin waxes,petrolatum wax, montan wax, ceresin, ozokerite, waxes from thedestructive or non-destructive hydrogenation of mineral oil, synthetichydrocarbon oil, shale oil, coal, and waxes produced synthetically bythe catalytic reaction of hydrocarbons, or waxes derived from themodified Fischer-Tropsch reaction of carbon monoxide and hydrogen. Theprocess of this invention is especially applicable in the separation ofwax mixtures containing color bodies and oil into a higher melting waxfraction of light color and low oil content, and a lower melting waxfraction of darker color and containing most of the oil originallypresent in the wax mixture.

In accordance with this invention, a wax-containing mixture is separatedinto fractions of higher and lower melting point by countercurrentlycontacting the wax-containing mixture in an extraction zone with anextraction solvent and a solvent, additive or additives at a temperaturesuch that two liquid phases are formed, one comprising the highermelting wax fraction with minor amounts of solvent and additive, and theother comprising the lower melting wax fraction with major amounts ofsolvent and additive, separating the liquid phases from one another, andremoving the solvent and additive from each. The extraction solventemployed may have a density less than that of the wax, while theadditive or additivesmay have a density greater than that of the wax.However, when the additive or additives are partially immiscible withthe extraction solvent and are less dense than such solvent or the wax,the additive or additives will flow countercurrent to the extractionsolvent and will appear with that liquid phase comprising the highermelting wax fraction. The success of the process depends upon thecontrol of the temperature throughout the extraction zone and upon theregulation of the proportions of solvent and additive used, and thepoints of introduction of the wax-containing mixture, the solvent, andthe additive into the extraction zone.

The extraction solvent may be defined as an agent which, when intimatelymixed with a waxcontaining mixture, forms two liquid phases or layers,one comprising a rafiinate phase contain ing mostly wax of highermelting point than the untreated wax and a portion of the solvent, andthe other comprising an extract phase containing mostly solvent, and waxof lower melting point than the untreated wax, as well as a major portion of the color bodies and oil originally present in the untreatedwax.

The solvent additive may be defined as an agent used in conjunction withthe extraction solvent for the purpose of modifying the characteristicsof the extraction solvent. The additive may lower the temperature atwhich solid wax precipitates out of the extraction solvent, or it mayraise the miscibility temperature of the extraction solvent with thewax. However, the additive chosen for a particular extraction solventmust not excessively lower the selectivity of the extraction solvent atthe temperature of extraction.

The extraction solvent may be employed in amounts ranging from 1 to 5volumes of solvent per volume of untreated wax stock, while the additiveor additives may be used in amounts ranging from 0.05 to 1 volume pervolume of untreated wax.

The extraction solvent which may be employed in accordance with thepresent invention comprises acetone.

The solvent additive or additives, which are usually employed in amountsconstituting not more than 50% by volume of the extraction solvent,comprise diethylene glycol.

The process of the present invention may be carried out in a multi-stagebatch countercurrent extraction system or in a continuous countercurrentextraction system, preferably a tower provided with perforated bafflesor containing a packing material such as ceramic shapes, tiles, metal\vool. or fragments of ceramic material, glass, pumice, Carborundum, orconcrete. For most efiective operation, a temperature gradient ismaintained in the system by means of. heating or cooling coils orjackets, the temperature increasing in the direction of flow of therafiinate or higher melting wax fraction.

The present invention may be further understood with rcfe ence to theaccompanying d awing which ill .tes diagrammatically a c nousextraction. system suitable for carrying out the process.

Referring to the drawing, a wax-containing mixture is continuouslyintroduced, in liquid condition, into the extraction tower I throughvalve controlled pipe 2 at a rate of 100 volumes per hour. An ext-rction solvent comprising acetone is continuously introduced from vessel3 by means of valve-controlled pipe 4 and manifold 5 into the lowersection of the tower above the rafiinate outlet at a rate of 400 volumesper hour. The first additive comprising diethylene glycol iscontinuously introduced from vessel 0 through valve-controlled pipe Einto the extraction tower i above the wax inlet at a rate of volumes perhour. The second additive also comprising diethylene glycol iscontinuously introduced from vessel 9 by valve-controlled pipe 8 intothe extraction tower l between the point of introduction of the firstadditive and the outlet of the extract phase, at a rate of 40 volumesper hour. An intimate countercurrent contacting of the wax stock, theextraction solvent, and the additives is effected in tower i, thetemperature being controlled in the tower by means of coils it throughwhich a heating or cooling medium is circulated as required. Thetemperature, in the present case, is held constant, for example, at 85the contents being entirely in the liquid phase. The wax stock, beingsubjected to the action of the solvent and additives, is caused toseparate by solvent action into two fractions, the higher meltingfraction wax passing downwardly through the tower together with a minoramount of dissolved extraction solvent and additive, and being withdrawntherefrom below the level of the dotted line !2 representing the highermelting wax phase relatively free of entrained, immiscible solvent andadditive. The rafiinate phase comprising the higher melting wax anddissolved solvent and additive is passed from the bottom of tower lthrough valve-controlled pipe lt into a vacuum evaporator or still Illwherein the solvent and additive are removed from the higher melting waxby vaporization, the solvent and additive vapors passing through pipe115 into fractionating tower It provided with a reboiler or heating coilli, while the higher melting wax is drawn from the bottom of evaporatori l delivered by valve-controlled pipe I8 into storage vessel 59. Suchwax fraction was white in color, and had a substantially higher meltingpoint and a lower oil content than the wax stock originally charged.

The extract phase comprising the lower melting wax fraction, colorbodies-oil, and the major portion of the extraction solvent andadditives is withdrawn from the upper section of tower i above the levelof the dotted line representing the extract phase relatively free ofentrained, higher melting wax. The extract phase is delivered byvalvecontrolled pipe 2i into a vacuum evaporator or still wherein thesolvent and additives are vaporized from the lower melting the latterbeing drawn from the bottom of the evaporator and passed byvalve-controlled pipe 23 to storage vessel 2 A. The lower melting waxwas brown in color and had a substantially lower melting point and ahigher oil content than the ori inal waxy mixture.

The solvent and additive vapors are passed from the top of evaporator 22through pipe 25 into fractionating tower 16, wherein such vaporstogether with those introduced through pipe l5, fractionated, theextraction solvent, i. e., acetone, being taken overhead as vaporthrough pipe 26, condensed in condenser 27 and returned by pipe 28 tosolvent storage vessel 3. A portion of the condensed solvent may bereturned to the top of tower it by valve-controlled pipe 29 as reflux.The additive, i. e., diethylene glycol, separated from the acetone byfractionation in tower I5, is taken from the bottom of tower It. asliquid, and is returned by pipes 3| and 30 to the additive storagevessels 6 and .0, respectively.

Depending upon the temperature of operation, the first additive may beintroduced somewhat below the point of introduction of the liquefied waxstock, for example, by means of valve-controlled pipe lli rather thanthrough valve-controlled pipe l, in which case the second additive maybe admitted through either or both of valvecontrolled pipes 7 and 8above the point of introduction of the wax stock. In general, theraffinate wax phase withdrawn from the extraction tower will containfrom 5% to 25% of solvent and additive, while the extract wax phase willcontain from 55% to of solvent and additive.

In the event that the extraction is to be carried out in a multi-stagebatch countercurrent system, for example, a four-stage system using thesolvent and additives specifically set forth above, the wax stock wouldbe introduced into the first stage extractor, the extraction solvent(acetone) would be introduced into the fourth stage extractor, and thefirst additive, i. e., diethylene glycol, would be introduced into thefirst stage extractor. The second additive, e. diethylene glycol, wouldbe introduced into the second stage extractor. The extract phase iswithdrawn from the first stage, while the rafiinate phase would beremoved from the fourth stage extractor. The temperature would increaseprogressively from the first stage to the fourth stage, using the waxystock, solvent, and additives described hereinabove. It is to beunderstood, of course, that the quantities and composition of thesolvent and of the additives may be varied within certain limits.

xemplary of the solvent and additive materials which may be used inaccordance with this invention is the following, the quantities beingvolumes per unit volume of wax stock.

Extraction Solvent 1st Additive 2nd Additive acetone, 4 d; 0.5

diethylene glycol, 0.4 diethylene glycol, 0.4 vols :l: 0.1 vols. :l: 0.1vols.

The present invention is further illustrated by the following example,which, however, is not to be construed as limiting the scope thereof.

(1) A slack wax having a melting point of 113 F. and an oil content of24.2% by weight was extracted in a system similar to that shown in theaccompanyin drawing, the extraction solvent comprising 4 volumes ofacetone, the first additive comprising 0.4 volume of diethylene glycol,and the second additive comprising 0.4 volume of diethylene glycol. Theslack wax was introduced into tower l by pipe 2, the solvent by pipe 4and manifold 5, the first additive by pipe 1 and the second additive bypipe 8. The temperaturein the extraction tower was maintained COB-r'stantat 85 F. After countercurrent contacting and removal of theramnate phase from the bottom of'the tower, and the extract phase fromthe top of the tower, the solvent and additives were recovered from thewax fractions by vacuum evaporation and fractionation. The results areshown in the following table:

Where the extraction operation is conducted in a tower, it has beenfound that a tower having a height of about 40 feet and a diameter of 6feet is satisfactory. The tower is provided with suitable packing towithin about 4 feet of the top and bottom thereof, such spacesfunctioning as quiescent zones in which entrained materials arepermitted to separate from the rafiinate and extract phases,respectively. In such a tower, the wax stock is charged at a point about13 feet from the top thereof, or approximately the distance from the topof the tower. The extraction solvent is charged just above the lowerlevel of the packing, for example, 3 to 4 feet from the bottom of thetower. The first additive may be introduced adjacent the point ofintroduction of the wax stock,

for example, 2 feet aboveor below the wax inlet. The second additive isintroduced approximately 2 feet above the point of introduction of thefirst additive. These values may be altered somewhat, depending upon thetower design, the solvent and additives used, and the temperaturesmaintained at various levels in the tower. The raflinate phase iswithdrawn from the bottom of the tower, and the extract phase from thetop thereof, the extraction solvent being less dense than the wax stock.

I claim:

1. The method of separating a wax-containing mixture'into fractions ofhigher and lower melting point, which comprises countercurrentlycontacting said Wax-containing mixture in an extraction zone with anextraction solvent and a solvent additive at a temperature such that twoimmiscible liquid phases are formed, one comprising the higher meltingwax fraction containing solvent and additive, and the other comprisingsolvent and additive and the lower melting wax fraction, separating thephases from one another, and removing the solvent and additive fromeach, the solvent being introduced into the extraction zone near thepoint of withdrawal of the higher melting wax fraction and the additivebe: ing introduced adjacent the point of introduction of thewax-containing mixture, the solvent comprising 3.5 to 4.5 volumes ofacetone per volume of wax-containing mixture, and the additivecomprising 0.3 to 0.5 volume of diethylene glycol per volume ofwax-containing mixture.

2. The method of separating a wax-containing mixture-into fractions ofhigher and lower melting point, which comprises countercurrentlycontacting said wax-containing mixture in an extraction zone with anextraction solvent and solvent additives at a temperature such that twoimmiscible liquid phases are formed, one comprising the higher meltingwax fraction'containing solvent and additives, and the other comprisingsolvent and additives and the lower melting wax fraction, separating thephases from one another, and removing the solvent and additives fromeach, the solvent being introduced into the extraction zone near thepoint of withdrawal of the higher melting wax fraction, the firstadditive bein introduced adjacent the point of introduction of thewax-containing mixture, and the second additive being introduced betweenthe point of introduction of the first additive and the point ofwithdrawal of the lower melting wax fraction, the solvent comprising 3.5to 4.5 volumes of acetone per volume of wax-containing mixture, thefirst additive comprising 0.3 to 0.5 volume of diethylene glycol pervolume of wax-containing mixture, and the second additive comprising 0.3to 0.5 volume of diethylene glycol per volume of wax-containing mixture.

3. The method of separating a wax-containing mixture into fractions ofhigher and lower melting point, which comprises countercurrentlycontacting said wax-containing" mixture in an extraction zone with anextraction solvent and a solvent additive at a temperature such that twoimmiscible liquid phases are formed, one comprising the higher meltingwax fraction with minor amounts of solvent and additive, and the othercomprising the lower melting wax fraction with major amounts of solventand additive, separating the phases from one another, and removing thesolvent and additive from each, the solvent being introduced into theextraction zone near the point of withdrawal of the higher melting waxfraction and the additive being introduced between the point ofwithdrawal of the lower melting wax fraction and the point ofintroduction of the wax-containing mixture, the solvent comprising 3.5to 4.5 volumes of acetone per volume of wax-containing mixture, and theadditive comprising 0.3 to 0.5 volume of diethylene glycol per volume ofwax-containing mixture.

4. The method of separating a wax-containing mixture into fractions ofhigher and lower melting point, which comprises countercurrentlycontacting said wax-containing mixture in an extraction zone with anextraction solvent and solvent additives at a temperature such that twoimmiscible liquid phases are formed, one comprising the higher meltingwax fraction with minor amounts of solvent and additives, and the othercomprising the lower melting wax fraction with major amounts of solventand additives, separating the phases from one another, and removing thesolvent and additives from each, the solvent being introduced into theextraction zone near the point of withdrawal of the higher melting waxfraction, the first additive being introduced between the point ofintroduction of the wax-containing mixture and the point of withdrawalof the lower melting wax fraction, and the second additive beingintroduced between the point of introduction of the first additive andthe point of withdrawal of the lower melting wax fraction, the solventcomprising 3.5 to 4.5 volumes of acetone per volume of wax-containingmixture, the first additive comprising 0.3 to 0.5 volume of diethyleneglycol per volume of waxcontaining mixture, and the second additivecomprising 0.3 to 0.5 volume of diethylene glycol per volume ofwax-containin mixture.

5. The method of separating a wax-containing mixture into fractions ofhigher and lower melting point, which comprises countercurrentlycontacting said wax-containing mixture in an-extraction zone with anextraction solvent and solvent additives at a temperature such that twoimmiscible liquid phases are formed, one comprising the higher meltingwax fraction containing solvent and additives, and the other comprisingsolvent and additives and the lower melting wax fraction, separating thephases from one another, and removing the solvent and additives fromeach, the solvent being introduced into the extraction zone near thepoint of withdrawal of the higher melting wax fraction, the firstadditive being introduced adjacent the point of introduction of thewax-containing mixture, and the second additive being introduced betweenthe point of introduction of the first additive and the point ofwithdrawal of the lower melting wax fraction, the solvent comprising 3.5to 4.5 volumes; of acetone. per volume of wax-containing EDGAR W.CLARKE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,017,432 Bahlke Oct. 15, 19352,141,511 Buchler et a1 Dec. 28, 1938 2,160,930 Whiteley et a1 June 6,1939

1. THE METHOD OF SEPARATING A WAX-CONTAINING MIXTURE INTO FRACTION OFHIGHER AND LOWER MELTING POINT, WHICH COMPRISES COUNTERCURRENTLYCONTACTING SAID WAX-CONTAINING MIXTURE IN AN EXTRACTION ZONE WITH ANEXTRACTION SOLVENT AND A SOLVENT ADDITIVE AT A TEMPERATURE SUCH THAT TWOIMMISCIBLE LIQUID PHASES ARE FORMED, ONE COMPRISING THE HIGHER MELTINGWAX FRACTION CONTAINING SOLVENT AND ADDITIVE, AND THE OTHER COMPRISINGSOLVENT AND ADDITIVE AND THE LOWER MELTING WAX FRACTION, SEPARATING THEPHASES FROM ONE ANOTHER, AND REMOVING THE SOLVENT AND ADDITIVE FROMEACH, THE SOLVENT BEING INTRODUCED INTO THE EXTRACTION ZONE NEAR THEPOINT OF WITHDRAWAL OF THE HIGHER MELTING WAX FRACTION AND THE ADDITIVEBEING INTRODUCED ADJACENT THE POINT OF INTRODUCTION